Stenus (Nestus) canalis, Ryvkin, 2012

Ryvkin, Alexandr B., 2012, New species and records of Stenus (Nestus) of the canaliculatus group, with the erection of a new species group (Insecta: Coleoptera: Staphylinidae: Steninae), European Journal of Taxonomy 13, pp. 1-62 : 30-32

Stenus (Nestus) canalis sp. nov.

( Figs. 4 C–D, 5E)

Stenus canaliculatus – Shavrin & Puthz 2007: 114 (pars).

Material examined

RUSSIA: Holotype: ♂, ‘ Magadan Area, Ten’kinskiy | District , Detrin River basin, | Vakkhanka Rill. Plateau : open | plots, soil traps. | 01– 11.06.1983. S.P. Bukhkalo [leg.]’ <printed label in Russian >, ‘HOLOTYPUS’ <my standard printed red label>, ‘ Stenus HT | canalis sp. n. | A.B. Ryvkin det., 2010’ <my standard determinative label> ( ZMMU) . Paratypes: 1 ♂, ‘ Magadan Area, Ten’kinskiy | District, near Sibit-Tyhellakh . | Dry birch forest. 14– 24.07.1982. | D.I. Berman [leg.]’ <printed label in Russian> ( AR) ; 1 ♂, ‘ Khabarovsk Territory, Jewish | Autonomous Area, Obluchenskiy | District, near Pashkovo. Puddle | bank under steep. | 05.07.1977. A.B. Ryvkin [leg.]’ <printed label in Russian>, ‘ Stenus | canaliculatus Gyll. | A.B. Ryvkin det. 1978’ ( AR) ; 1 ♂, ‘ Maritime Province, Khasan, | Golubinyi Utyos . | 4.viii. | 1991 S.A. Kurbatov [leg.]’ <photo label in Russian> ( AR) ; 1 ♂, ‘ Maritime Prov. | flood-plain of Poyma River | 30.07.–06.08.[19]99 | Shavrin A. [leg.]’ <printed label in Russian>, ‘ Stenus Gyll. | canaliculatus | det. V. Puthz 2005’ ( AR) ; 1 ♂, ‘Chita Area | NE side of Barun-Torey Lake | Myrgen Cape | 18– 19.06.1994 | V.[G.] Shilenkov leg.’ <printed label in Russian>, ‘ Stenus Gyll. | canaliculatus | det. V. Puthz 1999’ ( AR) ; 1 ♂, ‘5.08.[19]86 <transverse> | Buryatya | Zaigraevo[=Zaigrayevo] 1695 [=5695th km] st[ation] | Voincov[=Voinkov] A. [leg.]’ <printed label>, ‘3-23 | canal.’, ‘ Stenus | canaliculatus | Shavrin A. det. 2006’ ( ASh) . — The paratypes listed above are also provided with both ‘PARATYPUS’ printed red label and my standard determinative label (‘ Stenus | canalis sp. n. | A.B. Ryvkin det., 2010’) for each lot. — 1 ♀, Magadan Area, upper reaches of Kolyma River, 7 km NNE of Omsukchan , 10 Jul. 1980, O. Mashukova leg. <?> ( AR) ; 1 ♀, Magadan Area, upper reaches of Kolyma River, 5 km NE of Spornoye , 21 Jun. 1981, A. Ryabukhin leg. <?> ( AR) .

Differential diagnosis

This species is closely related to S. (N.) canaliculatus Gyllenhal, 1827 and differs from it by the smaller body size, by the much more irregular puncturation, by the less developed ground sculpture, by the posterior margin of 8th abdominal sternite, which is much more shallowly emarginated, and by the shape of the aedeagus. External differences from all the known species of the canaliculatus-group are given in the key below.

Etymology

The specific name is the Latin adjective ‘ canalis ’ (canine).

Description

LENGTH. 2.8–3.7 mm (the latter value for the paratype specimen with abdomen extended).

COLORATION. Pitchy black, distinctly bronze-coloured shining, with moderately long and dense yellowish-silvery pubescence. Legs pitchy black to brownish-black, tibial apices and tarsi somewhat lighter. Antennae dark brown, with 1 st segment black and 2 nd brownish-black; 1 st segment of maxillar palpi yellow, 2 nd brown, 3rd dark brown, with very base a bit lighter.

HEAD. About 1/8 to 1/6 broader than pronotum (46:41, all measurements, except where specifically indicated, are from the holotype), a little narrower than elytra between humeri (46:48), distinctly narrower than elytra in broadest part (46:55). Front feebly evenly convex to nearly flat, with very vague and shallow lateral depressions, distinguishable only between antennal tubercles and eyes and behind the tubercles. Puncturation dense and irregular, partly nonrugosely confluent, sometimes with small but evident smooth spots and strips situated both medially and laterally; average diameter of punctures in middle about as large as the greatest cross-section of antennal segment 3. Frontal slope before antennal fossae rather flat. Anterior margin of labrum with a small median notch. Antennae rather short, scarcely reaching middle 1/3 of pronotum. Length proportions of antennal segments 2–11 = 6:5:5:4:3:3:2:3:4:6; segments 9–10 slightly transverse (3:3.5, 4:4.5), the segment 11 distinctly elongate (6:4).

PRONOTUM. Somewhat longer than broad (45:41), broadest just before middle, narrowed feebly convexly towards anterior margin and concavely towards posterior one. Longitudinal median furrow sharp and deep, well-developed over entire length of disk as a rule, but less evident in some paratypes in anterior 1/3 as well as near both anterior and posterior margins. Laterobasal depressions very shallow, nearly vanishing. Puncturation rather deep and irregular, partly nonrugosely confluent but not forming long furrows; punctures somewhat larger on average than those of head; some bulging smooth interstices between punctures evidently smaller in diameter than surrounding punctures.

ELYTRA. About as broad as long (55:55) to a bit broader, much longer than pronotum (55:45), by suture a bit longer than pronotum (46:45). Humeral angles short, angularly rounded, lateral sides uniformly moderately divergent posteriorly (48:55). Humeral and sutural depressions very feeble to nearly absent. Puncturation larger in diameter and sparser, more regular than that of pronotal disk, as a rule nonconfluent, but individual furrows of merged punctures visible in some paratypes; interstices between punctures distinctly smaller than half average diameter of puncture.

LEGS. Fairly short; metatibia much longer than metatarsus (38: 27 in paratype from Magadan Area); segment 1 of metatarsi about as long as segment 5 (7: 7 in the same paratype).

ABDOMEN. Moderately convex, with well developed paratergites and two pairs of keels at bases of anterior visible tergites. Lateral sides of abdomen nearly parallel, feebly convergent in apical part. Posterior margin of tergite 7 with fine light fringe. Puncturation of anterior visible tergites comparable in average diameter of punctures to that of head but not so coarse and much more regular; denser laterally, medioposteriorly with some interstices comparable to diameter of punctures or larger.

MICROSCULPTURE. Variable in different specimens. Very fine mesh-like ground sculpture visible, as a rule, between punctures or by edges of punctures on elytra in humeral impressions and near suture, as well as on periocular parts of head; abdominal tergites quite smooth and glossy at least in their median parts.

MALE. Meso- and metatibiae without specific characters; 8 th abdominal sternite without conspicuous impressions and keels, its posterior margin with a very broad and shallow rounded emargination; abdominal sternite 9 as in Fig. 5E ; aedeagus as in Fig. 4C, D.

FEMALE. No reliable female specimens included in type series.

Remarks

Both the females listed were captured at localities from which no male material is known. Therefore, they are not included in the type series and their attribution to this new species remains questionable. This new species seems to replace S. (N.) canaliculatus Gyllenhal, 1827 in the southernmost and, in part, easternmost territories of E Siberia and the Far East. Additional material is necessary to ascertain the precise distribution of both species in the E Palaearctic.

Figures

Fig. 4. – A–B: Stenus (Nestus) canosus sp. nov.: ♂ (holotype). A. Aedeagus, ventral view. B. Apical part of aedeagus, ventral view. – C–D: S. (N.) canalis sp. nov.: ♂ (holotype). C. Aedeagus, ventral view. D. Apical part of aedeagus, ventral view. [Note that the difference in shape of the apical lobe compared to that in C is due to the level of magnification.] – Scales = 0.1 mm.

Fig. 5. ♂ copulative structures. A–E: Abdominal sternite 9. A. Stenus (Nestus) latipennis J. Sahlberg, 1880 (Russia: Krasnoyarsk Territory: Mirnoye). B. S. (N.) illusor Ryvkin, 1987 (Russia: Magadan Area: 2 km W of Splavnaya). C. S. (N.) delitor sp. nov. (holotype). D. S. (N.) canosus sp. nov. (holotype). E. S. (N.) canalis sp. nov. (holotype). F. S. (N.) caseyi Puthz, 1972 (U.S.A.: Michigan: Berrien Co.). Aedeagus, ventral view. – Scales = 0.1 mm.